This invention relates to a cylinder head for an internal combustion engine and more particularly to an improved cylinder head arrangement for a direct injected internal combustion engine.
In the interest of improving engine performance, both in terms of output and also improving fuel efficiency and exhaust emission control, direct cylinder injection offers a number of advantages. However, there is a distinct problem in connection with the positioning of the fuel injector so as to obtain the desired spray pattern in the combustion chamber and the desired relationship to the spark plug so as to ensure complete combustion within the combustion chamber.
The problems noted in the foregoing paragraph are particularly difficult when the engine employs multiple valves and associated intake passages that serve the valve seats. Specifically, it is difficult to position the fuel injector so that its spray pattern into the combustion chamber will offer either stratification and/or the formation of a homogeneous mixture under all or desired engine running conditions.
Also, the injector should be mounted in such a way that it will spray into the combustion chamber so as to minimize impact on the surfaces that define the combustion chamber. If the fuel impacts excessively on the combustion chamber surfaces, it may condense and not be completely burned during the combustion process.
It is also desirable to position the ignition plug at close to the geometric center of the combustion chamber, particularly at the top dead center condition. Unless this is done, then the flame propagation may be such that all portions of the fuel patch will not be burned during a particular combustion cycle.
Although multiple spark plugs can avoid some of these problems of incomplete combustion, they further complicate the cylinder head construction and thus are somewhat self-defeating in their nature.
It has been found that a particularly desirable location for the fuel injector, if a central spark plug is mounted in the cylinder head, is at a side of the cylinder head so that it injects toward the cylinder bore axis. Also if the injector is positioned away from the exhaust passages it will not be excessively heated. Generally, this dictates a positioning of the fuel injector in proximity to the intake ports that serve the combustion chamber and the passages associated therewith.
If the fuel injector is mounted so that it extends at an acute angle to the plane of the cylinder head surface that mates with the cylinder block to form the combustion chambers, the spray pattern can be directed generally downwardly toward the center of the cylinder bore axis and this will achieve many of the results desired. However, this places the fuel injector in a position where it will extend through the area where the intake or exhaust passages lie.
This interference with the intake and exhaust passages in the cylinder head results in the necessity for reshaping the passages and/or substantially reducing their flow area. In addition, this causes the tip of the fuel injector, which mates with the fuel rail for fuel supply, to be positioned in close proximity to the valve actuating mechanism. This is quite undesirable and can result in very complicated cylinder head arrangements.
Therefore, it has been proposed to mount the fuel injector so that it lies below the cylinder head passages and at an acute angle to the sealing surface of the cylinder head. In order to accomplish this, the associates passages are formed with a rather steep curvature so as to accommodate a central positioning of the fuel injector.
This is particularly true when there are a pair of intake passages or a Siamese intake passage that serves a pair of ports in the cylinder head on the side where the fuel injector is positioned. In such a situation, these passages are generally curved at a rather steep angle from the valve seats in a generally upward direction in order to clear the fuel injector. This gives rise to an effective reduction in the flow area and a flow restriction from the passages.
Furthermore, if the passages are intake passages, this curvature and their configuration may result in a flow pattern into the combustion chamber that is undesirable. Although some types of motion are desirable in connection with the inducted air, the particular flow pattern that will result from this upward curvature of the intake passages is not one that is particularly advantageous.
It is, therefore, a principal object of this invention to provide an improved cylinder head construction for an internal combustion engine that employs direct cylinder injection.
It is a further object of this invention to provide a cylinder head construction for an internal combustion engine wherein a fuel injector may be mounted below the intake passages toward the sealing surface of the cylinder head without requiring sharp curvatures in the passages that serve the adjacent valve ports.
It is a further object of this invention to provide a cylinder head construction having direct fuel injection wherein the fuel injector is juxtaposed to the intake passages, is positioned generally on a center side of the combustion chamber and the cylinder head intake passages are configured so as to have minimum curvature. That curvature that does exist is in the direction to give a swirling motion to the intake charge.
This invention is adapted to be embodied in a cylinder head for a direct injected internal combustion engine. The cylinder head has a sealing surface that is adapted to be held in sealing engagement with a cylinder block. Thus the cylinder head defines with a cylinder bore in that cylinder block a combustion chamber. A portion of the cylinder head sealing surface overlies the cylinder bore and defines at least a pair of valve seats on opposite sides of a first plane that extends through the center of the cylinder bore axis. Passages are formed in the cylinder head and extend from openings in outer side surfaces thereof to the respective valve seats. A fuel injector receiving opening is formed in one side of the cylinder head and opens through one of the side surfaces and terminates in a discharge nozzle opening that communicates with the cylinder head combustion chamber surface on a second plane that is perpendicular to the first plane and which also contains the cylinder bore axis. This fuel injector receiving opening is disposed beneath the passage at the one side of the cylinder head. That passage has an inlet opening in the outer surface and this inlet opening has a center lying substantially on the second plane and the passage is inclined at an acute angle to this second plane to its termination at the valve seat so that the injector opening is cleared without requiring sharp curvatures or substantial reduction in the flow area of the passage.